let isDone: boolean = false
let a1: number = 10
let a2: number = 0b101
let myName: string = 'Tom'
let myAge: number = 19
const info = `My name is ${myAge}, I am ${myAge} years old`
let u: undefined = undefined
let n: null = null
let list1: number[] = [1, 2, 3]
let list2: Array<number> = [1, 2, 3]
let t1: [string, number]
t1 = ['java', 10]
console.log(t1[0].substring(1))
// enum Color{
//     Red,Green,Blue
// }
enum Color {
    Red = 1,
    Green,
    Blue
}

let myColor: Color = Color.Blue
console.log(myColor, Color.Green)
let colorName: string = Color[1]
console.log(colorName)

let notSure: any = 4
notSure = 'maybe a string'
notSure = false

let list: any[] = [1, true, 'free']
list[1] = 100

/* 表示没有任何类型, 一般用来说明函数的返回值不能是undefined和null之外的值 */
function fn(): void {
    console.log('fn()')
    // return undefined
    // return null
    // return 1 // error
}

let unusable: void = undefined
